Proline at a glance

  • Amino acid used in the body’s synthesis of proteins
  • Considered a conditionally essential amino acid
  • Helps skin retain moisture
  • Supports structures that keep skin looking and feeling younger

Proline description

Proline is an amino acid that is used in the body’s synthesis of proteins. While the body can produce proline, its synthesis can be limited by certain physiological circumstances, which has led some scientists to refer to proline as a conditionally essential amino acid. In those circumstances, it must be consumed as part of a person’s diet for them to obtain the proper amount. Like all amino acids, proline helps skin retain moisture, adding to a supple look and feel. It also helps support structures that prevent the appearance of fine lines and wrinkles. As an amino acid, it is considered safe as used in cosmetics; in fact, proline is part of many peptides used in skin care. Forms of this amino acid, such as cocoyl proline, are typically used in concentrations between 0.1–5%.

Proline references

  • Amino Acids in Nutrition and Health, August 2020, pages 187-199
  • Current Medicinal Chemistry, December 2018, pages 5,512-5,527
  • PLoS ONE, February 2018, ePublication
  • International Journal of Cosmetic Science, August 2009, pages 327-345

Peer-reviewed, substantiated scientific research is used to assess ingredients in this dictionary. Regulations regarding constraints, permitted concentration levels and availability vary by country and region.

Ingredient ratings


Proven and supported by independent studies. Outstanding active ingredient for most skin types or concerns.


Necessary to improve a formula's texture, stability, or penetration.


Generally non-irritating but may have aesthetic, stability, or other issues that limit its usefulness.


There is a likelihood of irritation. Risk increases when combined with other problematic ingredients.


May cause irritation, inflammation, dryness, etc. May offer benefit in some capability but overall, proven to do more harm than good.


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Not Rated